Fully coupled solution of a two-phase model for laminar film condensation of vapor–gas mixtures in horizontal channels

Detailed results are presented for laminar film condensation of vapor–gas mixtures in horizontal flat-plate channels using a fully coupled implicit numerical approach that achieves excellent convergence behavior. These results correspond to steam–air and R134a–air mixtures over wide ranges of the independent parameters, and they include velocity, temperature, and gas concentration profiles, as well as axial variations of film thickness, pressure gradient and Nusselt number. Effects of the four independent variables (inlet values of gas concentration, Reynolds number and pressure, and the inlet-to-wall temperature difference) on the film thickness, pressure gradient, and the local and average Nusselt numbers are carefully examined. It was found that the condensation of R134a–air corresponds to thicker liquid films, lower heat transfer rates, and lower algebraic values of the pressure gradient when compared with steam–air at the same operating conditions.